Apparatus for the concentration of minerals



May 6, 1941. a. SBORLINO v APPARATUS FOR THE CONCENTRATION OF MINERALSFiled April 20, 1939 2 Sheets-Sheet 1 May 6, 1941.

e. SBORLINO 2,240,671 APPARATUS FOR THE CONCENTRATION OF MINERALS FiledApril 20, 1939 2 Sheets-Shea: 2

Jive/22% Giza/7) W Patented May a, 1941 UNITED STATES PATENT OFFICE2,240,671 APPARATUS FOR THE CONCENTRATION or MINERALS.

Gino Sborlino, Milan. Italy Application April 20, 1939, Serial No.269,027 In Italy May 5, 1938 5 Claims.

of the mechanically agitated type comprising an 5 upright agitatingchamber (preferably rectangular) having a horizontal rotary agitatornear the bottom of the chamber and having. a concentric funnel shapedvessel of such dimensions and located within the chamber so that thelower open 1 end of the funnel almost touches the blades of the agitatorwhilst the upper 'open end of this vessel has a diameter slightly lessthan that of theagitating chamber. Adjacent to this agitating chamberand separated from it by a solid wall, is a frothing chamber of thespitkasten-type connected to the agitating chamber by means of twoopenings in the said wall, an upper one communicating with the spaceoutside the funnel shape vessel and alower one near the bottom of thefrothing chamber communicating through a pipe. with the space inside thefunnel-shape vessel.

The main object of the present invention is to accelerate the flotationprocess and this object is oval shape withan 111 9 Opening of a diameterattained by creating in the said flotation apparatus two separate andindependent pulp circuits:

one, which may be termed the frothing circuit is set up between theagitating chamber and-the frothing chamber by means of the above menmtioned upper and lower communications between both chambers and itspurpose is to bring the agitated pulp rapidly and repeatedly out of theturbulent zone of the agitating chamber into the quiet zone in thefrothing chamber where the formation of the froth will not be disturbedor.

hindered.

The second pulp circuit which may be termed the aerating circuit" is setup in the agitating r chamber itself in sucha manner, that the interiorof the funnel shaped vessel is constantly kept empty by the suckingaction of the agitator whilst the pulp level in the agitating chamber.is kept at such a height that a thin veil of pulp is constantlycascading back into the interior of 4 the funnel thereby becomingsupersaturated with air like a waterfall.

Another object of this invention is to reduce the power consumption offlotation apparatus which object is attained firstly by the absence ofany baflies or grids in the agitating chamberwhich in other apparatus ofthis type prevents the free movement and flow of the ore pulp andthereby v causes increased power consumption-and secondly, by theagitator being shaped and mounted .75

in the apparatus like the impeller of a centrifugal The accompanyingdrawings illustrate by way of example several embodiments of theinvention in which:

Fig. 1- is an elevation partly in section of an apparatus constructed inaccordance with the invention;

Fig. 2 is a vertical transverse sectional view through one of theagitating chambers;-

Fig. 3 is a fragmentary detailed view partly in section of amodification of the invention;

Fig. 4 is a fragmentary perspective view of the device shown in Fig. 3;

Fig, 5 is an elevation partly in section of a modification of thearrangement shown in Figs. 1 and 2;

Fig. 6 is a top plan view of the arrangement shown in Fig. 5.

The agitating cham r I (Fig. 2) is of prismatic shape with rectangularcross-section but it can also be of cylindrical shape. ,gfrranged avessel 2 hereinafter referred to as a In this chamber is unnel, ofcylindrical or cylindrical-conical or only a little smaller than thatcfthe agitating chamber I whilst the lower end opens into the impeller l.at its lower'end has a bell-shaped rim 3-;

The impeller-shaf-tis coaxial with the funnel and is provided at itslower end with an impeller 4. This. impeller consists of a horizontaldisc proyided on its upper side with blades of suitable shape, theclearance between the upper edges of these blades and the bell shapedrim 3 being such as to create the conditions prevailing in a centrifugalpump in which the funnel acts as suction pipe and the space between thefunnel and the walls of the agitating chamber serves as the discharge.pipe.

The agitating chamber has a slot 6 through which it communicates with afrothing charnber 5. The latter has an opening at its lower pointed endto which is attached a pipe I which establishes communication betweenthe frothing chamber and the interior of the funnel. Another similarpipe I2 is .provided for the introduction of pulp from another adjacentflotation cell.

The slot 6 is provided with a gate 8 suspended in the agitation chamber,adjacent to the wall which I can be lowered and raised by means of aspindle and a handwheel 9 and thus the extent of the slot-opening can beregulated at will, the gate being only suspended adjacent to the wall,the

hydrodynamic pressure of the stream of pulp passing from the agitatingto the frothing chambers will keep the gate in constant close contactwith the wall thus obviating the necessity of guide grooves which easilybecome choked by deposits of ore particles.

One side-wall of the agitating chamber is fitted with an overflow slotI3 (Fig. 1) the height of the overflow being adjustable by a weir l3.

This overflow slot l3 communicates with a box I and from this box a pipe20 leads to the feedfunnel I! of an adjacent agitating box, In thismanner a number of cells'or flotation units can be united to form amultiple cell-unit.

The impeller 4 is made of a wear-resisting material, and the bell shapedrim 3 is provided on its underside with a wear resisting andinterchangeable liner; likewise the bottom and the walls of theagitating chamber I are protected by interchangeable wearing plates.

Thehorizontal disc of the impeller is provided with several circularholes and its underside is also equipped with curved blades of smallheight which suck air through the holes beating it into the pulp insmall bubbles. The function of the above described apparatus can beexplained as follows:

Considering -a single cell only which is filled with ore-pulp introducedthrough the channel I! into the agitating chamber and in which theimpeller 4 is rotated in the proper sense and with the proper speed, itwill be noted that the pulp contained in the funnel 2 is sucked oil andis pumped into the space outside the funnel; assuming the slot 6 to becompletely closed by the sliding gate 8 a circulation of the ore-pulpcontained in the agitating chamber will take place starting from theimpeller passing through the space between funnel and walls of theagitating chambers and overflowing the rim of the funnel back to theimpeller. With proper speed and shape of the impeller a condition ofequilibrium will be reached characterized by the funnel being constantlysucked empty of pulp.

If it be assumed that through the feed-pipe l2 a constant flow of pulpis passing into the agitating chamber, then the position of theadjustable weir l3 will determine the quantity of pulp which will becirculated in the manner set out above and which can be regulated atwill within the pumping capacity of the impeller.

In the foregoing explanation of the pulp-circuit in the agitatingchamber, it has been assumed that the slot 6 is completely closed by thesliding gate 8.

If however, this slot 6 be partially or completely opened then a certainquantity of pulp will pass through this slot 6 into the frothing chamber5 and f1 am there back through the channel I into the funnel 2. a

The height of the pulp-level in the agitating chamber depends on therelation between the cross sectional areas of slot 6 and channel I; if,v

for instance, this relation be such that through both orifices equalquantities of pulp pass per unit of time, then the pulp level in thefrothing-chamber will adjust itself at such a height that h (Fig. 2),equals ha. From this it becomes clear that by varying the free crosssectional area of slot 6 by means of sliding gate 8 the pulp level inthe frothing chamber can be kept constant at each height because thepulp level in the agitatingchamber remains constant as set out above.

From the foregoing description it becomes evident that any pulp streamentering the agitating chamber by the channel I! and leaving it by theoverflow-weir I3 is subject during its passage to two circulations: onethrough the funnel and another through the frothing chamber bothcirculations not being dependent in some mechanical means but beingsolely created by hydrostatic pressure which can be kept constant by thesimple means of keeping constant the speed of rotation of impeller 4 andwhich can moreover be easily regulated and varied.

This double circuit of the pulp as set out in the foregoing descriptionconstitutes a big advantage of the present invention over other knownfiotation apparatus of a similar type and for the following reasons:

(1) The aerated pulp circulates so rapidly from the agitating chamberinto the frothing chamber that the air beaten into the pulp getsreleased only after the pulp has entered the frothing chamber and hasbecome quiescent; the air released near the entrance of the frothingchamber rises in a multitude of line bubbles to the pulp surface and thesame conditions prevail as in flotation apparatus of the pneumatic typei. e. a very rapid flotation with the production of a brittle and ratherdirty bubble column. The ever newly forming froth pushes the bubblecolumn towards the overflow end of the frothing chamber and during thistravel the bubble column cleans itself by breaking down and condensinginto a very clean and rather dry froth.

(2) The quantity of pulp circulating between the agitating chamber andfrothing chamber can be kept very large and can be made a multiple ofthe pulp fed to the apparatus, This has the great advantage that thechances for all even the most reluctantly floating mineral particles toenter into the froth and to be thus recovered are many timesgreater-than in other known apparatus of similar type.

(3) The aeration of the flotation pulp is much more intensive than inother apparatus of similar type because in addition to the air sucked inby the impeller 4 through the empty funnel 2 a large quantity of finelydisseminated air is drawn into the pulp during its cascading over therim of the funnel back into its interior, because the pulp is spread outinto a thin moving sheet of extremely large surface and it is a knownfact that in this way a rapid saturation of the pulp with air isaccomplished.

(4) The aeration of the pulp can be regulated within wide limits byraising or lowering the overflow weir l3 whereby the pulp-overflow backinto the funnel can be increased or reduced or entirely suppressed ifthe pulp level in the agitating chamber is lowered below the upper edgeof funnel 2. Together with the aeration, also the agitation of the pulpcan be regulated which is of importance for the so called conditioningof the pulp.

(5) The total quantity of pulp entering the flotation apparatus iscompelled to circulate several times through the same frothing chamberwhereby the maximum recovery is obtained and any short-circuiting" isrendered impossible.

(6) The pulp level in each frothing chamber can be raised or lowered atwill and in each frothing chamber independently of the pulp'level in thepreceding or following chamber by a simple adjustment of the slidinggate.

In this way the thickness of the froth layer can be regulated in eachfrothing chamber according is established above I completely by raisingit a wet light and rather dirty froth can be produced.

(7) The funnel 2 in the agitating chamber acts as a support for thevortex set up by the rotation of theimpeller and any. irregular whirlingof the pulps is thus .avoided. In this way a considerable saving inpoweris effected in comparison with flotation apparatus of similar type notprovided with this funnel. (8) On account of the intensive aeration ef-1 fected by the continuous cascading of the pulp through the funnel 2 itis rendered possible to lower the speed of rotationof the impellerconsiderably below that considered up to the present as the criticalspeed (500-550 meters per minute). This of course entails a furthersaving in power.

(9) Due to the gravity flow of the pulp through the apparatus and thecomplete absence of any suction-trans ort of the pulp, it is possible tostart the apparatus after a shu -down without having previously to cleanthe apparatus 'of the settled solids.

The flotation apparatus can be modified from that set out in theforegoing description, viz.

(0.) Instead of the overflow-opening l3 regulated by weir l3 for thepassage of the pulp from the agitating chamber to the next one, a vessel[8 (Figs. 3and 4), can be provided in the funnel 2 alongside of and nearits upper edge, which is covered by two sliding launders 2| (Fig. 4) andby shifting these launders the inlet opening of this vessel can beenlarged or reduced at will. The" pulp stream entering the agitatingchamber being constant, it follows that by reducing the inlet opening ofvessel IS the pulp level in the agitating 35 chamber will rise untilsuch a hydrostatic head the upper edge of the funnel as will be requiredto maintain a constant flow of the pulp through the agitatingchambereven with the restricted inlet opening of vessel [8; This higherhydrostatic head will also cause a heavier overflow of pulp back intothe funnel and in this way the aeration of the pulp can be regulated atThe pulp leaving the agitating chamber by way of the vessel l8 passesfrom there through the channel l9 (Fig. 4) to the next agitating chamheras alreadyset forth earlier.

(17) Instead of conducting the pulp from one agitating chamber throughchannel I: into the bottom part of the funnel 2 of the next agitatingchamber (use can be made of the hydrostatic head hi prevailing in oneagitating chamber) to inject the pulp'through a sloping and closedchannel 20, Figs. 5 and 6, into the next fr'othing chamber, the pulpissuing from this slot will be attained.

The intensively aerated pulp passes in this way and rapidly through eachunit cell and before leaving eachunitcell it circulates several times byway of slot 6 and channel 1 through the 0 agitating chamber.

This manner of conducting the pulp can be ap- I plied in combinationwith oneor the other of the devices set out earlier for the outlet ofthe pulp from the agitating chamber. 5

(c) For the treatment of ores rich in flotable minerals or in mineralsfloating only reluctantly, or, when saving in floor spaceis aimed at,each agitating chamber can be fitted with a second frothing chamber 5'arranged symmetrically to frothing chamber 5 and slot 6'. and channel Iwill establish the communication of this frothing chamber 5 with thetagitating chamber.

The impeller 4 has to be adapted in this case to the higher pumping dutyrequired and witha slightly higher power consumption thecapacity' ofeach unit can be doubled in certain cases.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is:

l. A flotation apparatus comprising a froth chamber, anagitating-chamber separated from said froth chamber by a vertical wall,a rotary vertical shaft extending through said agitating chamber, animpeller mounted on the shaft adjacent the bottom of the agitatingchamber, a

funnel, shaped vessel in the agitating chamber and coaxial with theshaft and extending upwardly from adjacent the impeller, the wallbetween the froth chamber and agitationchamber being provided with anopening in its upper portion and below the top of the funnel shapedvessel, and a pipe extending from the lower part of the froth chamber tothe interior of the funnel shaped vessel. i

.2. A flotationapparatus comprising a froth chamber, anagitating chamberseparated from said froth chamber bya vertical wall, a rotary verticalshaft extending through said agitating chamber, an impeller mounted ontheshaft adjacent the bottom of the agitatingicii amber; a funnel shapedvessel in the agitating chamber and coaxial with the shaft and extendingupwardly from adjacent the impeller, the wall between the froth cham berand agitation chamber being provided with/a horizontal slotted openingin its upper portio funnel shaped vessel, and a pipe extendingfrom thelower part of the froth chamber to the interior ofthe funnel shapedvessel and said vessel having a bell-shaped outward flaring rim on'itslower edge, adjacent peller blades. 3 I p 3. A flotation apparatusaccording to claim 1, in which the funnel shaped vessel has at its upperedge a diameter of at least 40 percent of the inside width of theagitating chamber, and in which the height of the said funnel shapedvessel is only a little less than that of the said agitating chamber andvery close to the height of the frothdischarge lip of the said frothingchamber.

4. A flotation apparatus according to claim 2, in which the saidhorizontal slotted opening in the upper portion of the agitating chamberhas a cross-sectional area of between one and a half and five times thatof the pipe extending from the lower part of the froth chamber to" theinterior of the funnel shaped vessel. I

5. A flotation apparatus according to claim 2, in which the saidhorizontal slotted opening in the upper portion of the, agitatingchamber is provided with a sliding gate'suspendedfrom above and movableby means of hinged levers and manual means forvarying the freecross-sectional area of said horizontal slotted opening.

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and below the top of thethe upper edges of the im-

